Fighting The Effects Of Corrosion In Fuel Systems

Don’t Let Corrosion Cause Your Engine to Fail

Corrosion can be a killer in your vehicle’s fuel system. That’s actually been documented: corrosion and related contamination have been identified among the most common causes of fuel pump failure1. And corrosion doesn’t just attack the fuel pump. It can also damage other metal components and lead to clogged fuel injectors or carburetor jets. Protecting your fuel system from the damaging effects of corrosion is essential to your vehicle’s reliability and performance.

 

To understand why, let’s look at what corrosion is and what it does. Corrosion is a chemical  process that converts a metal to an oxide or other stable compound. For example, rust is the common name given to iron oxide. Corrosion is accelerated by the presence of water and can result in material loss. 

Gasoline becomes contaminated with water during transportation and storage. Additional water forms as temperature variations cause moisture in the air to condense in a vehicle’s fuel tank.  Without ethanol, gasoline can hold about 150 ppm (parts per-million) of dissolved water at 70⁰ F. However, modern pump gasoline is commonly treated with 10% ethanol, which increases the water holding capacity of the fuel by up to 4,600 % (6000 – 7000ppm @ 70⁰ F).

 

As fuel cools – for example, overnight – its water holding capacity is decreased. Once the water present in the fuel exceeds the fuel’s holding capacity, the water separates from the fuel and forms a layer or phase, a process called phase separation. The water is then free to attack fuel system components.

 

The corrosive effects of water have both direct and indirect impacts on vehicle performance. The direct effect is the formation of oxides, hydroxides, and sulfides that can lead to material loss and weakening. In addition to material loss, stable oxide layers can form on system components and contribute to lost performance and component failures. 

Copper oxides form on brass surfaces in carburetors and may clog carburetor jets or cause floats to stick, resulting in rough idle, hesitation, and other drivability issues. In fuel-injected vehicles, the same copper oxides can form on electrical contacts in the fuel pump, causing it to run hotter, which reduces pump life. What’s more, fuel level sensors can become covered in a silver oxide layer that causes the fuel gauge to fail or operate erratically.

The indirect effects of corrosion are the result of the oxides, hydroxide, and sulfide products of corrosion contaminating the fuel system. For example, as water corrodes the fuel tank and other metal fuel system components, oxides form and contaminate the fuel with hard particles.

 

Fuel system contamination with solid particles can lead to fuel pump failures, hard or long start conditions, rough idle, and failure to start. Solid particulates may clog the fuel pump’s intake screen, starving the pump of fuel, leading to pump overheating and, eventually, failure. If the particulate makes it past the pick-up screen, it can result in increased pump wear. Larger particles may even jam the pump, resulting in a sudden pump failure.  As the particulate passes out of the pump, it can become stuck in the pump’s check valve leading to a loss of hold pressure and long or difficult starting.

 

Contamination that makes it out of the fuel pump can still result in significant issues. Excessive corrosion can clog fuel filters and starve the vehicle of fuel. Corrosion not captured by the fuel filter, or in lines downstream from the filter, can become stuck in screens intended to protect the fuel injectors, causing a loss of engine efficiency, power, and drivability.

 

 

Many fuel system components are made of corrosion resistant or coated materials. However, no protection is perfect, and over time even modern materials corrode, which can lead to vehicle failure.

 

 

You get the picture: persistent corrosion in the fuel system can cause, at a minimum, inconvenient performance issues, and left unchecked can cause costly engine failure. And the problem is especially acute in older vehicles with a lot of miles. That is why we recommend using Techron® High Mileage Fuel System Cleaner every 1,000 miles2 in classic vehicles and those with over 75,000 miles. Techron High Mileage is specifically formulated with multiple corrosion inhibitors and advanced fuel detergents to protect your investment and keep your vehicle performing. 

 

 

1.  Gordon, Jacques Fuel Pump 101: The Basics of Fuel Pump Diagnosis and Repair. Auto Service Professional 24 October 2017

2.  Do not exceed 12 doses between oil changes. 

Sean Lantz
Sean Lantz is Chevron’s product technical specialist for North American passenger car motor oils and specialty products. He also provides technical support to Chevron’s ISOCLEAN and after market fuel additives programs. He holds an MS in Mechanical Engineering from the University of California, Merced and prior to joining Chevron lubricants he worked in automotive powertrain development and as a plant engineer.